PubMed Health⌕ Search

Biomedical subjects

Keith Bley

Publications and source records attributed to Keith Bley.

4 recordsLinked to original sources
PubMed2005

Toxicity studies with pure trans-capsaicin delivered to dogs via intravenous administration.

Previous toxicology and pharmacology studies have reported variable acute cardiac effects of capsaicin, primarily involving hypotension and bradycardia. However, these studies have suffered from two important limitations. First, the capsaicin tested has been derived from pepper plant extracts, which is likely to display varying degrees of purity and possibly diverse impurity profiles. Second, post-dosing follow-up was generally limited to three or fewer days. Therefore, the objective of the studies reported here was to test the cardiac and other target organ toxicity potential of pure, synthetic trans-capsaicin (the only naturally occurring stereoisomer of capsaicin) when delivered via intravenous administration to dogs either acutely or for 14 days. Taken together, results from these two studies indicate that pure trans--capsaicin--even when delivered directly into the systemic circulation at high dose levels--is rapidly eliminated, induces transient tachycardia and hypertension, does not alter the duration of cardiac action potentials, and causes only very minimal organ toxicities. The different toxicity profiles of pure trans-capsaicin reported here and chili pepper extracts previously reported suggest that the purity and source of capsaicin should be an important consideration for toxicological evaluations.

Animals↗
PubMed2004

Genotoxicity studies with pure trans-capsaicin.

Both positive and negative effects have been found in classical genetic toxicology assays with capsaicin. However, the capsaicin tested in most studies has been derived from pepper plant extracts, which is likely to display varying degrees of purity and possibly diverse impurity profiles. Therefore, the objective of the series of studies reported here was to test the genotoxic potential of pure, synthetic trans-capsaicin (the only naturally occurring geometric isomer of capsaicin), using four genotoxicity assays widely used to evaluate drug substances. These included the Ames, mouse lymphoma cell mutation, mouse in vivo bone marrow micronucleus and chromosomal aberration in human peripheral blood lymphocytes (HPBL) assays. In the Ames assay, pure trans-capsaicin was not mutagenic to Salmonella typhimurium or Escherichia coli when dissolved in dimethylsulfoxide and tested at concentrations extending into the toxic range. trans-Capsaicin was weakly mutagenic in mouse lymphoma L5178Y cells, in the presence of S9 mix, when dissolved in dimethylsulfoxide and tested at concentrations extending into the toxic range. Limited evidence for very weak activity was also obtained in the absence of S9 mix. trans-Capsaicin did not induce micronuclei in bone marrow cells when tested to the maximum tolerated dose of 800 mg/kg per day in male and 200 mg/kg per day in female CD-1 mice using a 0 h plus 24 h oral dosing and 48 h sampling regimen. Finally, trans-capsaicin did not induce structural or numerical chromosomal aberrations when evaluated for its ability to induce clastogenicity in blood lymphocytes. Taken together, these data suggest that the genotoxic potential of pure trans-capsaicin is very low, especially as the clinical significance of weak mutagenicity in the mouse lymphoma assay for catechol-moiety containing compounds is unclear. Moreover, the different genotoxicity profiles of pure trans-capsaicin and purified chili pepper extracts suggest that the purity and source of capsaicin should always be an important consideration for toxicological evaluations.

Animals↗
PubMedDate not supplied

Developmental toxicity study of pure trans-capsaicin in rats and rabbits.

Human environmental and dietary exposure to trans-capsaicin--the pungent ingredient in chili peppers--is ubiquitous. Moreover, based on the highly selective agonism of trans-capsaicin for TRPV1 receptors, drug products containing high concentrations of trans-capsaicin are under development as analgesics. For instance, a high-concentration (8% w/w) pure trans-capsaicin dermal patch (designated NGX-4010) is in advanced clinical evaluation for the management of neuropathic pain of peripheral origin. Our objective was to investigate effects of trans-capsaicin on embryo/fetal development, consequent to maternal exposure, from implantation to closure of the hard palate. trans-Capsaicin was delivered systemically by means of either a patch [NGX-4010 (25, 37.5, or 50 cm(2))] to pregnant Sprague-Dawley rats on days of presumed gestation (DGs) 7 through 17, or via a 10% w/v capsaicin liquid formulation (CLF), at dosages of 3, 6.5 or 13 mul/cm(2) applied to a 200-cm(2) area on the back on DGs 7 though 19 to timed-mated New Zealand white rabbits. In rats, the maternal no-observable-effect level (NOEL) was less than 25 cm(2) but no cesarean-sectioning or litter parameters were affected by application of NGX-4010 at patch sizes as high as 50 cm(2). The only test article-related observations were delays in skeletal ossification, evident as significant reductions in the average number of metatarsals and ossified hindlimb and forelimb phalanges that occurred in the 50 cm(2) NGX-4010 dose group. Although the values for ossified metatarsals were outside the historical control range, ossified hindlimb and forelimb phalanges were within historical control ranges. No other gross external, soft tissue, or skeletal fetal alterations (malformations or variations) were caused by application of the NGX-4010. In rabbits, the maternal NOEL was less than 3 mul/cm(2) CLF (or 0.3 mg/cm(2)trans-capsaicin) per 200 cm(2), but no cesarean-sectioning or litter parameters were affected. No fetal alterations (malformations or variations) were caused by dosages of CLF as high as 13 mul/cm(2) (or 1.3 mg/cm(2)trans-capsaicin). Taken together, these data suggest that tran s-capsaicin should not be considered a developmental toxicant.

Administration, Cutaneous↗